To investigate the role of leukocytes and neutrophils in the peripheral blood on airway responsiveness, we studied nine patients with chronic bronchitis and histologically proved bronchial carcinoma before and after chemotherapy. The concentration of methacholine (in mg/ml) necessary to increase specific airway resistance by 100%, PC100SRaw, and the number of leukocytes and neutrophils (in cells x 10(6)/ml) were measured before, and 8 and 16 days after chemotherapy. Mean (SEM) total number of leukocytes decreased significantly (p less than 0.001) from 9.0 (0.8) to 4.4 (0.6) and 3.4 (0.4), and mean (SEM) number of neutrophils decreased significantly (p less than 0.005) from 5.1 (0.7) to 2.8 (0.5) and 1.0 (0.4), respectively. Mean (SEM) PC100SRaw was 3.3 (0.9) at baseline and 3.5 (1.2) and 3.8 (1.0) mg/ml at Days 8 and 16, respectively, without significant differences. These data suggest that a significant chemotherapy-induced leukocyte depletion in the peripheral blood does not influence airway responsiveness in patients with chronic bronchitis and bronchial carcinoma.